ELECTRONIC ABSORPTION-SPECTROSCOPY OF DIATOMICS ON A DYNAMIC SURFACE - IBR ON MGO(001)

A model for computing the absorption spectrum of a diatomic adsorbed o n a nonzero temperature surface is developed based on the exact time-d ependent expression for the absorption spectrum averaged over the surf ace variables. The required time evolution of the dipole transition de nsity operator is modeled by a quantum Langevin-type equation derived by the method of Caldeira and Leggett. The resultant equation is treat ed numerically and sample spectra are obtained for IBr on an MgO(001) surface at a temperature of 150 K. The results, parameterized by a dia tom-surface coupling constant, characterize the broadening of the spec trum in the presence of the stochastic thermal substrate motion. (C) 1 996 American Institute of Physics.